1. Field
One embodiment of the invention relates to a disk device, and more particularly, to a disk device using a recording medium of a perpendicular magnetic recording system.
2. Description of the Related Art
A disk device, for example, a magnetic disk device includes a rectangular box-shaped case. The case accommodates a magnetic disk as a magnetic recording medium, a spindle motor as drive means for supporting and rotating the magnetic disk, a plurality of magnetic heads for writing and reading out information to and from the magnetic disk, a head actuator for movably supporting the magnetic heads with respect to the magnetic disk, a voice coil motor for rotating and positioning the head actuator, a substrate unit having head ICs, and the like.
Recently, a perpendicular magnetic recording method is under development to increase a recording density. A magnetic disk device to which the perpendicular magnetic recording method is applied ordinarily includes a head disk assembly having a single magnetic pole head and a two-layered disk-shaped recording medium. The magnetic disk device is liable to be affected by the disturbance of a magnetic field from the outside, and there is confirmed a phenomenon that data recorded on the disk-shaped recording medium is deleted by the disturbance of the magnetic field. Thus, the magnetic disk device using the perpendicular magnetic recording method is required to more improve a shield function to an external magnetic field than a magnetic disk device using a conventional in-plane magnetic recording method. To fulfill the above requirement, in the disk device disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2003-77266, the shield function is improved by winding a tape-shaped or foil-shaped magnetic shield material on the upper surface, the lower surface, and the side surface of a case, in particular, on a region confronting with the moving range of a magnetic head. Otherwise, there is proposed a disk device whose shield property is improved by winding a permeability steel sheet on the outer surface of a case.
However, when the tape-shaped or foil-shaped magnetic shield member or the steel sheet formed in a predetermined shape is wound on the outer surface of the case of a magnetic disk device, the reduction in thickness and size of which is required, the thickness of the device is increased in its entirety and prevents the device from being thinned. When the magnetic shield member is wound, the number of parts is increased as well as it becomes troublesome to manufacture and assemble the device, and thus manufacturing cost is increased.